1. Field of the Invention
The present invention relates to a mobile station for performing communication using a specific communication system, and a communication system selection method thereof.
2. Related Background Art
Technologies to perform communication under specific conditions with priority, including communication using a specific communication system such as HSDPA (High-Speed Downlink Packet Access) and HSUPA (High-Speed Uplink Packet Access), and communication via a specific base station subject to better radio conditions, are under consideration. For example, Japanese Patent Application Laid-Open No. 2006-148587 discloses a mobile station which changes a switching destination to a specific basic station with priority if the radio conditions of this specific base station are better than an active base station.
According to this mobile station, if a received signal level of radio waves from an active base station is a specific level or higher when monitoring base stations of which radio conditions are better, only the received signal levels of radio waves from neighboring base stations that can support packet communication notified by a broadcast information sent from this base station are measured, and measurement of received signal levels of radio waves from neighboring base stations which do not support packet communication is omitted. By this, power consumption at cell switching time in a mobile station is decreased.
According to the technology disclosed in Japanese Patent Application Laid-Open No. 2006-148587, if there is a specific base station of which radio conditions are better, the cell where the mobile station exists can be switched to the cell under this specific base station with priority. However, it is not judged whether communication using such a specific communication method as HSDPA or HSUPA is possible or not in this switching destination cell.
Since it is judged whether a cell is switched or not only by radio conditions, a mobile station may not be able to camp on a cell in which communication using a specific communication system, such as HSDPA or HSUPA, is possible, even if the mobile station exists in a position where camping on is possible.